Centralized traffic controlling system for railroads



T. J. JUDGE April 25, 1939.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Mai-ch26,i957 INVENTO: if. f,

ATTOR'NEY Tmu Lo tcou 8 Patented Apr. 25, 1939 UNITED STATES PATENTOFFIQE CENTRALIZED TRAFFIC CONTROLLING SYSTElVI FOR RAILROADS ter, N. Y.

Application March 26,

7 Claims.

This invention relates to centralized traffic controlling systems forrailroads, and more particularly pertains to a system of the typeemploying direct line wire for control of the switches and signals.

One of the objects of the present invention is to provide means forcontrolling a call-on signal over the same line circuit provided for thecontrol of the main signals in a manner which c0- 10 relates the mainand call-on signals in a most desirable combination.

Other objects, purposes, and characteristic features of the presentinvention will be in part obvious from the accompanying drawing and inpart pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to theaccompanying drawing which is a diagrammatic illustration of oneembodiment of the present invention as applied to the control of traflicover a single railroad track switch.

Although the present invention may be applied to the control of signalsassociated with any type of track layout involving conflicting routesand non-conflicting routes as well as various other conditionsencountered in signalling practice, it has been specifically illustratedas applied to the control of the signals over a single track switch,which switch and signals are assumed to be associated with an automaticblock signal system of some suitable type, such for example, asdisclosed in the pending application of S. N. Wight, Ser. No. 120,423,filed July 3, 1926, now U. S. Patent 2,082,436, granted June 1, 1937,although the details of such a block signalling system have not beenshown.

For the purpose of simplifying the illustration and facilitating in theexplanation, the various parts and circuits constituting the embodimentof the invention have been shown diagrammatically and certainconventional illustrations have been employed, the drawing having beenmade more with the purpose of making it easy to understand theprinciples and mode of operation, than with the idea of illustrating thespecific construction and arrangement of parts that would be employed inpractice. Thus, the various relays and contacts have been illustrated ina conventional manner and symbols have been used to indicate theconnection to terminals of batteries, or other sources of electriccurrent instead of showing all of the wiring connections to thoseterminals.

The symbols and are employed to indicate the positive and negativeterminals respectively of suitable batteries or other sources of 1937,Serial No. 133,224

direct current; and the circuits with which these symbols are usedalways have current flowing in the same direction. The symbols (13+) and(B-) indicate connections to the opposite terminals of a suitablebattery or other direct cur-' rent source which has a central orintermediate tap designated (CN) and the circuits with which thesesymbols are used may have current flowing in one direction or the otherdepending upon the particular terminal used in combination with theintermediate tap (CN). It is to be further understood that in the eventalternating current should be desired, suitable means may be employed toaccomplish the control by alternating current within the scope of thepresent invention, and that the positive and negative terminalsindicated by the symbols may then be considered as indicating therelative instantaneous polarities.

With reference to the accompanying drawing,

a railroad track switch TS is illustrated as connecting the rails 4 of amain track to the rails 5 of a diverging or turn out track. This trackswitch TS is operated by a power driven switch machine SM which may beof any suitable type,

such, for example, as disclosed in the patent'to W. K. Howe, Pat. No.1,466,903, dated September 4, 1923, with the control of the motor ofsuch a switch machine being preferably provided as disclosed in thepatent to W. H. Hoppe et al., Pat. No. 1,877,876, dated September 20,1932. This switch machine SM may also be provided with a dual controlselector to permit hand operation of the track switch as shown, forexample, in the patent to W. K. Howe, Pat. No. 1,852,573, dated April 5,1932.

The control of the switch machine SM is governed by a switch machinecontrol lever SML located in a central office over a suitable linecircuit arrangement properly interrelated with the signal controls asgoverned by the signal lever SGL, all of which may be provided asdisclosed in my prior application, Ser. No. 741,626, filed August 27,1934.

In other words, the present invention may be considered as an improvedsignal control to provide for the control of a call-on signal in amanher which may be readily applied to the system shown in my abovementioned prior application, Ser. No. 741,626, filed August 27, 1934.

The main track adjacent the track switch TS and a portion of thediverging track to the fouling point comprises a detector track circuitwith the usual track battery and track relay T The main track is alsodivided into certain other track track battery and track relays of whichtrack relays T T and T are shown. Each of these track circuits is of theclosed circuit type and is insulated from the rest of the track by theusual insulated joints.

Trafiic over the track switch TS in an east bound direction is governedby the signals EA and IE on the main track and onto the diverging trackrespectively; while signals 2A and 3A are provided for governing trafficin an east bound direction on the main track and off the diverging trackrespectively.

A call-on signal I C is provided to allow the passage of east boundtrafiic over either the main track or the turn out track whenever themain signals governing such routes can not be cleared, due to thepresence of a train in advance of such signals. Similarly, call-onsignals 26 and 3C are provided to allow the passage of west boundtrafiic over either the main track or off the turn track when theassociated main signals cannot be cleared due to the presence of a trainin advance of such signals.

Associated with the signal IA is a home-distant relay IAHD. Similarly, ahome distant relay IBHD is associated with the signal IB, and a homedistant relay 23HD is associated with the signals 2A and 3A. Each ofthese home distant relays is of the usual polar neutral type and isoverned in accordance with trafiic conditions in advance of theirrespective signals in such a manner that they are energized with onepolarity or the other dependent upon the clear or caution indication ofthe next signal in advance governing traffic in the same direction, andare deenergized whenever there is intervening .trafiic. The control ofthese home distant relays has not been illustrated in detail as suchcontrol is well known to those skilled in the art and has been shown,for example, in the above mentioned application of S. N. Wight, Ser. No.120,423, filed July 3, 1926.

The track switch TS and the switch machine SM are preferably providedwith point detector contacts (not shown), as shown, for example, in thepatent to C. S. Bushnell, Pat. No. 1,517,236, dated November 25, 1924.These point detector contacts are employed to energize a switch positionindicating relay WP of the usual polar neutral type with one polaritywhen the track switch is in an extreme normal lock position, and toenergize it with the opposite polarity when the track switch is in anextreme reverse lock position, or to deenergize this relay WP wheneverthe track switch TS is unlocked or the switch machine SM is inoperation. Such control of the relay WP is well understood and is merelyindicated by a dotted line extending from the relay WP to the trackswitch TS and the switch machine SM. In this connection it is to beunderstood that certain of the signal circuits illustrated herein wouldprobably in actual practice be selected on correspondence relays insteadof directly upon the relay WP, which selections have been shown indetail in my above mentioned prior application, Ser. No. 741,626, butfor the sake of simplicity in giving an understanding of the presentinvention, only the relay WP has been shown herein. However, as abovementioned, the principles of the present invention may be readilyapplied to the system of my prior application.

A polar neutral relay GZ of the retained type is governed from thecontrol ofiice over a polarized control line circuit including the linewire 8. Such a retained-polar-neutral relay has been disclosed in theprior Pat. No. 1,852,210 dated April 5, 1932', granted to F. C. Larson.This type of relay is distinctively responsive to positive or negativeenergization but does not drop its neutral contacts upon a quickreversal of such polar energization by reason of the retaining windingwhich is inductively coupled to the main windings of the relay. Althoughsuch a relay has been employed for the purpose of disclosing the presentinvention, it is to be understood that various other devices andarrangements may be employed and still accomplish the purposes of thepresent invention.

Relays LD, RD and CD cooperate with the relay GZ for controlling theleft, right and call-0n signals respectively by selecting the circuitsfor signal controlling relays IAG, IBG, ICG, ZAG, 20G, SAG, and 30G.These signal controlling relays are associated with the respectivesignals as indicated by their characteristic reference characters andcause their respective signals to display red or danger indicationswhenever the corresponding G relays are deenergized and to display greenor yellow proceed indications whenever a corresponding G relay isenergized only if the trafiic conditions are proper.

Although the control of the signals has been in part illustrated and inpart indicated, it is to be understood that such control may includeconventional stick signals, or signals illuminated only upon approach,or signals having some other well known feature, without departing fromthe scope of the present invention. It is also to be understood thatvarious features of approach locking and time release may be providedfor the track switch as disclosed for example, in the prior applicationof R. M. Phinney, Ser. No. 463,- 940, filed June 26, 1930, now U. S.Patent 2,082,- 741 granted June 1, 1937. However, all such features ofinterrelationship between the switch TS and the signals has been omittedfor the sake of simplicity.

ra various other features so as to make the signals In the centralofiice, a suitable control machine is provided with the usual miniaturetrack diagram corresponding to the track layout in the field andassociated with which are the control levers. The switch control leverSML and signal control lever SGL for the track switch TS have been shownassociated with the miniature track switch ts. Associated with thesignal lever SGL is a call-on push button CPB for providing thedistinctive control of the call-on signals as hereinafter described indetail.

It is believed that further description of the' present invention fromthe standpoint of typical operations will best set forth itscharacteristic features.

OPERATION Normal c nditions.-With the various track sections unoccupied,the track relays T T T and T are normally energized. The signal leverSGL is assumed to be in a central or stop positicn so that all of thesignals are indicating stop.

parent upon consideration of the details of those circuits shown.

More specifically, the relay IAHD is provided with a circuit from (CN),through the windings of relay IAI-ID, front contact is of track relay Tfront contact I! of track relay T front contact I 8 of track relay Tthrough the remaining selections to the signal next in advance toreceive positive (3+) or negative (B) potential in accordance with theclear or caution indication of such signal.

A circuit for the relay IBHD is closed from (CN) through the windings ofrelay lBHD, front contact I 9 of track relay T through the remainingselections to the next signal in advance on the turn out track toreceive (B+) or (B-) depending upon whether the next signal in advanceis at clear or caution respectively.

The relay ZSI-ID is energized by a circuit closed from (CN), throughwindings of relay 2311]), front contact 2!! of track relay T frontcontact 2! of track relay T through the remaining selections up to thenext signal in advance to receive (B+) or (B) depending upon the clearor caution indication of such signal.

Manual control of the track switch.The track switch TS is power operatedby the switch machine SM under the control of the operator by lever SMLsubject to proper locking to prevent the track switch TS from beingmoved to a new position when it is unsafe to do so. For example, thetrack switch TS can not be operated to a new position by the operationof the lever SML whenever the signal control lever SGL has been operatedto a signal clearing position, nor can the movement of the lever SML toa new position under such circumstances be effective to operate thetrack switch when the lever SGL is restored to its stop position. Inother words, the lever SML must be in-a position corresponding to theposition of the track switch TS while the lever SGL is in its central orstop position before a new operation of the track switch. TS can beeffected. This has been conveniently termed the electric lock equivalentand has been shown and described in my above mentioned application, Ser.No. 741,626, filed August 27, 1934. Similarly, under certain conditionsthe track switch TS should not be operated until a pre-determined timesubsequent to the return of the governing signals to stop conditionswhile a train is approaching such signals. To accomplish such purpose, asuitable time delay means is provided to be effective as disclosed inthe above mentioned prior application of R. M. Phinney, No. 463,940,filed June 26, 1936.

All of these features are well known to those skilled in the art, buthave been mentioned in connection with the present disclosure for thepurpose of bringing out the purpose and utility of the call-on signalsof the present invention.

Main signal control.-With the track switch TS in a normal position forthe passage of main line traffic, either the signal lA or the signal 2Acan be cleared depending upon whether the signal control lever SGL isactuated to the right or to the left respectively.

When the lever SGL is operated to the right, the signal control linecircuit is energized with energy from (B-), through a circuit includingfront contact 39 of call-on push button CPB, signal contro1 levercontact 6 in a left hand position, windings of relay GZZ, line wire 8,front contact 3! of track relay T windings of relay GZ, to (CN).

Such energization of the relay GZ causes its polar contacts to beoperated to the left followed by the picking up of its neutral contacts.This closes an energizing circuit for the signal control relay RD fromthrough a circuit including front contact 32 of relay GZ, polar contact33 of relay GZ in a left hand position, back contact 34 of relay LD,windings of relay RD, to

As soon as the relay RD picks up, it closes a stick circuit from througha circuit including a front contact 32 of relay GZ, front contact 35 ofrelay RD, windings of relay RD, to

The picking up of the relay RD completes an energizing circuit for therelay IAG from through a circuit including polar contact 36 of relay GZin a left hand position, front contact 31 of relay RD, back contact 38of relay CD, front contact 39 of relay WP, polar contact M! of relay WPin a right hand position, front contact 4| of relay IAHD, windings ofrelay IAG, to

The picking up of the contact 42 of relay IAG causes the signal M tochange its indication from stop to clear or caution depending upon theposition of polar contact 43 of the relay lAI-ID. It is readily apparentthat this signal IA may be returned to stop by restoring the lever SGLto its central position.

If the lever SGL is operated to the left, relay G2 is energized over acircuit closed from (B+) through a circuit including front contact 44 ofcall-on push button CPB, lever contact 6 in a right hand position,windings of relay GZZ, line wire 8, front contact 3!! of track relay Tmain windings of relay G2, to (ON).

Such energization causes the polar contacts of the relay GZ to operateto the right and followed by the picking up of its neutral contacts.This closes an energizing circuit for the relay LD from through acircuit including front contact 32 of relay GZ, polar contact 33 ofrelay GZ in a right hand position, back contact 45 of relay RD, windingsof relay LD, to

As soon as the relay LD picks up, it closes a stick circuit from througha circuit including front contact 32 of relay GZ, front contact 45 ofrelay LD, windings of relay LD, to

The picking up of the relay LD closes an energizing circuit for therelay ZAG from through a circuit including polar contact 35 of relay GZin a right hand position, front contact 4-! of relay LD, back contact 48of relay CD, front contact 69 of relay WP, polar contact 50 of relay W?in a right hand position, front contact 5| of relay 23HD, windings ofrelay ZAG, to

{Ihe picking up of contact 52 of relay ZAG causes the signal 2A tochange its indication from stop to clear or caution depending upon theposition of polar contact 53 of relay 2?;I-ID.

It is, of course, obvious that the return of the lever SGL to a centralposition causes the return of the signal 2A to stop.

Assuming that the track switch TS has been operated to a reverseposition which is indicated by the proper responses of relay WP, theneither the signal B or the signal 3A may be cleared by the actuation ofthe lever SGL to the right or to the left respectively.

If the lever SGL is operated to the right under such circumstances, thenthe relay GZ is energized with negative potential, as above described,causing the relay RD to be picked up. This causes the energization ofthe relay iBG by a circuit closed from through a circuit including polarcontact 36 of relay G2 in a left hand position, front contact 3'1 ofrelay RD, back contact 38 of relay CD, front contact 39 of relay WP,

ill)

'polar contact 40 of relay WP in a left hand position, front contact 54of relay lBHD, windings of relay IBG, to

The picking up of contact 55 of relay iBG causes the indication of thesignal IE to change from stop to clear or caution depending upon theposition of the polar contact 56 of the relay IBHD.

It is, of course, apparent that the signal IB can be returned to stop bythe restoration of the signal lever SGL to its central or stop position.

If the lever SGL is operated to the left with the track switch TS in areverse position, then the relay GZ is energized with positivepotential, as above described, so that the relay LD is picked up. Thiscloses an energizing circuit for the relay 3AG from through a circuitincluding polar contact 36 of relay GZ in a right hand position, frontcontact 41 of relay LD, back contact 48 of relay CD, front contact 19 ofrelay WP, polar contact'59 of relay WP in a left hand position, frontcontact of relay 23I-ID, windings of relay 3AG, to

The picking up of contact 58 of relay SAG causes the signal 3A to changeits indication from stop to clear or caution depending upon the positionof the polar contact 59 of relay 23HD.

It is, of course, obvious that the signal 3A may be returned to stop bythe return of the signal lever SGL'to its central or stop position.

Call-on signal controL-There are times when a first train, as a westbound train, is beyond a main signal, such as signal 2A, for example, asufficient distance to allow a second, west bound, train to pass overthe track switch TS, and then make a back up move onto the turnout trackWithout waiting for the first train to pass beyond the next signal inadvance. Obviously, in a centralized trafiic controlling system wheretrains are entirely governed by signal indication, such second traincould not proceed over the track switch because the signal 2A can not becleared with relay 23HD deenergized by reason of the occupied conditionof the track section including relay T But the present inventionprovides that a call-on signal under such circumstances may be clearedby proper manipulation of the signal lever SGL and call-on push buttonCPB.

Assuming such circumstances, the operator would move the signal leverSGL to its left hand position and noting that the main signal does notclear by reason of the failure of a suitable signal indication forsignal 2A to be displayed on the control panel (by means not shown butcontemplated as employed in connection with the present invention asdisclosed in my prior application No. 741,626), he then momentarilyoperates the call-on push button CPB followed by its selfrestoration toits normal position.

While the call-on push button CPB is actuated, the original positivepolarity (13+) placed upon the signal control line circuit through frontcontact 44 of push button CPB is reversed so that negative potential isapplied through back contact 44. Such reversal of polarity on the relayGZ causes it to actuate its polar contacts to left hand positions, butas this reversal is accomplished relatively fast, the neutral contactsof the relay GZ remain picked up.

The actuation of the signal lever SGL to the left and the initialenergization of the relay GZ caused the relay LD to be picked up withthe polar contact 33 in a right hand position, but such relatively quickreversal of the polarity on the relay GZ by button CPB causes the polarcontact 33 to be a'otuatedto the left although the neutral contact 32 ofthe relay GZ is still picked up maintaining the stick circuit of therelay LD.

Thus, as soon'as the polar contact 33 reaches a left hand position, apick up'circuit is closed for the relay CD from through a circuitincluding front contact 32 of relay GZ, polar contact 33 of relay GZ ina left hand position, front contact 34 of relay LD, windings of relayCD, to The relay CD immediately picks up closing a stick circuit fromthrough a circuit including front contact 32 of relay GZ, front contact6b of relay CD, windings of relay CD, to

Upon the release of the push button CPB, the polarity on the relay GZrestores to the original polarity applied by the lever SGL in a lefthand position, but the relatively quick reversaloccurs without droppingthe neutral contact 32 of the relay GZ so that both the relays LD and CDare maintained picked up through their stick circuits.

The picking up of the relay CD closes an energizing circuit for therelay ZCG from through a circuit including polar contact 36 of relay GZin a right hand position, front contact 41 of relay LD, front contact 48of relay CD, front contact iii of relay WP, polar contact 62 of relay WPin a right hand position, back contact 53 of relay ZAG, windings ofrelay 206, to

The picking up of contact 54 of relay 20G causes the signal 20 to changeits indication from stop to clear so that the train may pass over thetrack switch TS subject to the rules or instructions given to trainmenwith regard to proceeding on permission of a call-on signal, such as,for example, being prepared to stop upon sight of an obstruction.

After the train has passed over the track switch TS and beyond thesignal 5A, the track switch TS may be caused to operate to a reverseposition so that the train may proceed in accordance with the indicationof signal 13 or signal lC onto the turn out track.

It will be noted in connection with the above description, that thecall-on signal 2C cannot be clearedunless the signal 2A is at stop byreason of the inclusion of the back contact 63 of relay 2AG in theenergizing circuit of the relay ZCG, but once the call-on signal iscleared such call-on signal is entirely under the control of theoperator and the signal 2A cannot in any way automatically clear uponthe passage of the first train beyond the governing block section. Thisis because of the open condition of the circuit for relay ZAG at backcontact 48 of relay CD.

It is also noted that a call-on signal can not be cleared unless theoperator first endeavors to clear the corresponding main or high speedsignal by the proper manipulation of the lever SGL, (and if the mainsignal is not held .at stop by traffic,'it may clear, but a longoperation of the push button CPB, relay CD picks up, to cause the mainsignal to go to stop) and the continued clear condition of a callon isdependent upon the signal lever SGL remaining in this main sig-- nalclearing position, while the putting to stop of either a main or call-onsignal is accomplished by the same operation, namely, the return of thelever SGL to its stop position.

It will be readily apparent that the picking up of the relay CD by theoperation of the call-on push button CPB while the signal lever SGL-isin a left hand position with the track switch TS in a reverse positioncauses the energization of the relay 30G by reason of a circuit closedfrom through a circuit including polar contact 36 of relay GZ in a righthand position, front contact 4'! of relay LD, front contact 48 of relayCD, front contact Bl of relay WP, polar contact 62 of relay WP in a lefthand position, back contact 65 of relay BAG, windings of relay 3CG, toThe picking up of contact 65 of relay SCG changes the indication of thesignal 30 from stop to clear. It is, of course, obvious that the returnof the signal lever SGL to its stop position restores such signal tostop.

There is another condition under which a callon signal is particularlyuseful in connection with the remote control of trains by signalindication. For example, a first train may be standing upon the tracksection associated with relay T so that the home distant relay IAHD isdeenergized opening front contact 4!. This prevents the operator fromclearing the signal IA to allow a second train to proceed past suchsignal to connect with the first train. In fact, it would be undesirableto clear a high speed signal, such as signal IA, with a train standingon such track section, but the clearing of the call-on signal 10 withits limited speed restrictions, readily permits a second train toproceed past signal K; to connect with the first train standing on thetrack section T Let us assume that the operator actuates the signallever SGL to the right while a first train is on the track sectionassociated with relay T This causes negative potential to be applied tothe relay GZ actuating its polar contacts to the left and picking up itsneutral contacts so that the relay ED is picked up, but the relay IAGcan not be picked up for reasons above pointed out, namely, the opencondition of front contact t i. The operator then actuates the call-onpush button CPB, momentarily reversing the polarity applied to the relayGZ to close a circuit for the relay CD from through a circuit includingfront contact 32 of relay GZ, polar contact of relay 33 in a right handposition, front contact 45 of relay RD, windings of relay CD, to As soonas the relay CD is picked up, its stick circuit is closed so that therelease of the push button CPB and the consequent reversal of polarityon the relay GZ do not effect the dropping of either RD or CD, but doesaccomplish the clearing of the call-on signal 50 by the energization ofthe relay ICG over a circuit closed from through. a circuit includingpolar contact 36 of relay G2 in a left hand position, front contact 31of relay RD, front contact 38 of relay CD, front contact 6? of relay WP,back contact 58 of relay lAG, back contact 69 of relay IBG, windings ofrelay ECG, to The picking up of contact ill of relay I CG changes theindication of the signal 50 from stop to clear. It is, of course,obvious that the return of the signal lever SGL to its center or stopposition causes the relay G to be returned to stop.

It is noted that in order to pick up the relay iCG to clear the signallC, both of the signals 1A and IB must be at stop by reason of backcontacts 68 and 39 of relays !AG and IBG respectively. Also, the trackswitch TS must be looked as indicated by the energized condition andclosure of front contact 91 of relay WP, although the call-on signal maybe cleared with the track switch TS in either normal or reverseposition.

Under each of the conditions above assumed for the clearing of a call-onsignal, it is apparent that the main signal is held at stopautomatically by the presence of a train, but if there is no train tohold the main signal at stop, the operation of the cal1-on push buttonCPB causes such main signal to be put to stop and the callon signal tobe cleared by reason of the picking up of the relay CD.

It is also being noted in connection with the control of call-on signalsthat a double reversal of polarity is required in order to clear acall-on signal. In other words, a. single reversal of polarity resultsin the clearing of no signal at all. For example, should the operatoractuate the signal lever SGL to the right and then changing his mindquickly operate it to the left, a quick reversal of polarity would occuron the relay GZ but such reversal of polarity would first pick up therelay RD and then the relay CD, but the relay GZ would then be energizedwith positive potential'so that its contacts would be to the right, sothat it would result in clearing no signal. In brief, the polarityrequired on the relay GZ in order to clear a signal must be the initialpolarity and the double reversal is required in order to accomplishthis. This feature also provides that the operator can not ill-advisedlyhold the button CPB down while he actuates the lever SGL to the right orto the left and thereafter release the relay CPB and obtain a call-onsignal. He will neither get the call-on nor the main signal in such acircumstance.

Track: indication-The signal control line circuit includes front contact3! of the track relay 'I so that the signal can not be cleared while atrain is on the detector track section and also provides for meanswhereby the presence or passage of a train over the detector tracksection can be indicated in the central office.

More specifically, whenever the signal lever SGL is in an operatedposition to clear a signal and a train accepts such cleared signal, thenthe opening of contact 3| deenergizes the relay GZZ. Such deenergizationof the relay (322 can be employed to provide control for a trackoccupancy indicator in any suitable way, as shown for a similarlydesignated relay in my prior application No. 741,626, filed August 27,1934, as well as for the other purposes disclosed in such priorapplication. The contacts l2 and 29 of relay GZZ correspond respectivelyto the contacts with the same reference characters in such priorapplication to which reference may be made for a typical control forproviding such an indication.

In this connection, it is to be noted that the features of the presentinvention are assumed to be applicable as an improvement upon the systemof the prior application so that with the circuit arrangements disclosedtherein modified in accordance with the present invention, the operationof the relay GZZ in combination with the operations disclosed in suchprior application may readily accomplish the purposes disclosed therein.However, it is thought to be suflicient for an understanding of thepresent invention and the manner in which an electro-responsive meansmay act in the central office for the control of suitable indicators andthe like to merely indicate by a legend on the drawing that the relayG22 may accomplish the control of a track occupancy indicator in anysuitable manner known in the art. In other Words, such control of anindicator need not be the same as shown in my prior application but maybe as shown in the patent, No. 1,794,594, granted March 3, 1931, to F.L. Dodgson.

Although only one specific embodiment of the invention has beendisclosed and although it has been mentioned that the principles of thepresent invention may be applied to the system of my prior applicationNo. 741,626, it is to be understood that the principles of the presentinvention may be applied to various other types of systems where thepolarized line circuit is employed for the control of the signals.

Having described a trafiic controlling system as one specific embodimentof the present invention, it is desired to be understood that this formis selected to facilitate in the disclosure of the present invention,rather than to limit the number of forms which it may assume, and it isto be further understood that various modifications, adaptations andalterations may be applied to the specific form shown to meet therequirements of practice without in any manner departing from the spiritor scope of the present invention, except as limited by the appendedclaims.

Having described my invention, I now claim:

1. In a centralized traffic controlling system for railroads; a mainsignal and a call-on signal; a retained-neutral-polar relay controlledover a polarized line circuit; a main signal relay; a callon signalrelay; a pick-up circuit for said main signal relay closed when saidretained-neutralpolar relay is energized with one polarity; a stickcircuit for said main signal relay including a front contact of saidmain signal relay and a front contact of said retained-neutral-polarrelay; a pick-up circuit for said call-on signal relay including a frontcontact of said main signal relay and closed when saidretained-neutralpolar relay is energized with the opposite polarity; astick circuit for said call-on signal relay including a front contact ofsaid call-on signal relay and a front contact of saidretained-neutral-polar relay; a control circuit for said main signalincluding a front contact of said main signal relay and a polar contactof said retainedneutral-polar relay closed when saidretainedneutral-polar relay is energized with said one polarity; and acontrol circuit for said call-on signal including a front contact ofsaid main signal relay, a front contact of said call-on signal relay,and a polar contact of said retainedneutral-polar relay closed when saidretainedneutral-polar relay is energized with said one polarity.

2. In a centralized trafiic controlling system for railroads, a railroadtrack switch, main signals for controlling trafiic over said trackswitch in both of its positions for both directions, call-n signals forcontrolling traffic over said track switch in both of its positions forboth directions, a line circuit extending from said track switch to acontrol ofiice, a control lever at the office for energizing said linecircuit with one polarity or the other and for deenergizing said linecircuit,a manually operable push button for causing a double reversal inpolarity of the energization of said line circuit as determined by saidcontrol lever, a retained-neutral-polar relay included in series in saidline circuit at said track switch, circuit means for clearing theparticular main signal for the route determined by the position of theswitch for one direction when said retainedneutral-polar relay isenergized with one polarity, circuit means for energizing the particularmain signal for the route determined by the position of the switch forthe opposite direction when said retained-neutral-polar relay isenergized clearing the particular call-on signal for the routedetermined by the position of the switch for one direction or the otherin accordance with the initial polarity of energization of said linecircuit as repeated by said retained-neutral-polar relay only after adouble reversal in polarity of the energization of said line circuitwith said reversals each occurring sufliciently quickly to maintainclosed the front contact of said retained-neutral-polar relay.

3. In a centralized traffic controlling system for railroads, a mainsignal and a call-on signal, a control oilice, a line circuit connectingsaid signals with the control office, relay means for controlling saidmain signal to indicate clear and stop, respectively, by energizationand deenergization of said line circuit, and means for clearing saidcall-on signal by only a double reversal in polarity of the energizationof said line circuit when the separate reversals are effected withoutleaving the line deenergized a period of time as long as the operatingtime of part of said relay means, said signals requiring continuedenergization of the line circuit for their continued clear indication.

4. In a centralized trafiic controlling system for railroads, a controloifice, a line circuit connecting the control oflice with a remotelocation, two trafiic controlling devices at the remote location, meansfor energizing and deenergizing one of said devices by energization anddeenergization respectively of said line circuit, and means forenergizing the other of said devices by only a double reversal inpolarity of the energization of said line circuit, and with eachreversal efiected without leaving the line deenergized for more than apredetermined time, said devices requiring continued energization of theline circuit for their continued energization.

5. In a centralized traffic controlling system. for railroads, a controloffice, a line circuit connecting the control office with a remotestation, two trafiic controlling devices at the remote station, acontrol lever at the office for energizing said line circuit withcurrent of one or the other polarity or deenergizing said line circuit,other control means at the ofiice for causing a relatively quick doublereversal in polarity of the energization of said line circuit asdetermined by said lever, electro-responsive means at the stationresponsive to the energization and the deenergization of said linecircuit for respectively distinctively controlling one of said trafliccontrolling devices, the electro-responsive means being slower torespond to deenergization of the line circuit than the time requiredduring each of said double reversal of polarity when the line circuit isdeenergized, and means at the station controlled by saidelectro-responsive means in response to a double reversal in polarity ofthe energization of said line circuit for controlling the other of saidtraffic controlling devices.

6. In a centralized trailic controlling system for railroads, a group ofsignals, means for selectively controlling the signals by thedistinctive polarized energization of a retained-neutral-polar relay,manual meansfor controlling the energization of the relay, other trafficcontrolling means, and control circuits for said other means operativeonly upon a double reversal in polarity of the energization of saidretained-neutral-polar relay when the deenergized periods of theretained-neutral-polar relay occurring upon each said reversal is lessthan the releasing time for such polar relay, said signals all becomingdeenergized upon the polar relay becoming deenergized for a time equalto its releasing time.

"I. In a centralized traflic controlling system for railroads, a controloflice, a main signal and a call-on signal for governing trafiic over astretch of track, a line circuit extending between said signals and thecontrol office, slow acting means for distinctively controlling saidmain signal by energization and deenergization respectively of said linecircuit, means including said slow acting means for controlling saidcall-0n signal by only a double reversal in polarity of the energizationof said line circuit, with the deenergization period of the line circuitoccurring upon each said reversal not continuing as long as the time forthe slow acting means to respond to a deenergization, deenergization ofthe line circuit for a time as long as the time for the slow actingmeans to respond to a deenergization deenergizing the signals, and meansfor indicating in the control ofirce the entrance of a train into saidstretch of track by deenergization of said line circuit at a time whensuch line circuit is energized to control either said main signal orsaid call-on signal.

THOMAS J. JUDGE.

